The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives, which impart or assist in imparting a negative charge to the toner resin particles and enable toners with rapid admix characteristics. In one embodiment, there are provided in accordance with the present invention toner compositions comprised of resin particles, pigment particles, and clay or clay-like charge additives. In one embodiment, the present invention is directed to toners with charge additives of synthetic anionic clays or minerals that contain exchangeable anions. These materials encompass, for example, the layered double hydroxides or mixed metal hydroxides of the general formula EQU M.sub.a.sup.2+ M.sub.b.sup.3+ (OH).sub.2a+2b (X.sup.n-).sub.2/n.xH.sub.2 O
where M.sup.2+ may be Mg.sup.2+, Fe.sup.2+, Co.sup.2+, Ni.sup.2+, Zn.sup.2+, and the like; M.sup.3+ may be Al.sup.3+, Cr.sup.3+, Fe.sup.3+, and the like; and X may be any anion such as a halide Cl.sup.-, Br.sup.-, l.sup.-, and the like, a pseudohalide such as NCS-, N.sub.3 - and the like, other inorganic anions such as SO.sub.4.sup.2-, NO.sub.3.sup.2-, CO.sub.3.sup.2-, PO.sub.4.sup.3-, and the like, organic anions such as salicylate, lauryl sulfate, dodecylsulfonate, terephthalate, and the like, polyoxometalate anions such as (Mo.sub.7 O.sub.24).sup.6-, (W.sub.7 O.sub.24).sup.6-, (V.sub.10 O.sub.28).sup.6- and the like, polyoxometalate anions of the Keggin type structure such as .alpha.-(H.sub.2 W.sub.12 O.sub.40).sup.6-, .alpha.-(SiV.sub.3 W.sub.9 O.sub.40).sup.7- and the like; n is the charge on the anion which in embodiments would generally range from 1 to about 4; a and b are subscripts indicating the amount of metal in the divalent and trivalent states; a may, for example, range from 1 to about 6 while b may, for example, range from 1 to about 3; and X may, for example, range from 0 to about 6. These materials also include the hydrotalcites which can be considered mixed metal hydroxides of the formulas Mg.sub.6 Al.sub.2 (OH).sub.16 CO.sub.3.4H.sub.2 O, Mg.sub.4.5 Al.sub.2 (OH).sub.13 (CO.sub.3) and Mg.sub.4.5 Al.sub.2 (OH).sub.11 (CO.sub.3).sub.0.8 O.sub.0.2. Structurally, these materials can be considered as being comprised of positively charged brucite-like layers of [Mg.sub.6 Al.sub.2 (OH).sub.16 ].sup.2+ and negatively charged interlayers of 4H.sub.2 O and [CO.sub.3 ].sup.2-, and wherein the interlayer carbonate ions are exchangeable, for example, with a halide such as chloride. The aforementioned additives in embodiments of the present invention enable, for example, toners with rapid admix of less than about 60 seconds, extended developer life, stable electrical properties, and high image print quality with substantially no background deposits. Also, the aforementioned toner compositions usually contain pigment particles comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, or brown components, or mixtures thereof, thereby providing for the development and generation of black and/or colored images. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic imaging and printing processes, including color processes.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner resin, are well known. Thus, for example, there is described in U.S. Pat. Nos. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions; 4,221,856 which discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R radicals are hydrocarbons having from 8 to about 22 carbon atoms, and each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion, for example sulfate, sulfonate, nitrate, borate, chlorate, and the halogens such as iodide, chloride and bromide, reference the Abstract of the Disclosure and column 3; a similar teaching is presented in U.S. Pat. No. 4,312,933 which is a division of U.S. Pat. No. 4,291,111; and similar teachings are presented in U.S. Pat. No. 4,291,112 wherein A is an anion including, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also, there is disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there is disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430 and 4,560,635 which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271 a complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include U.S. Pat. Nos. 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives.
Disclosed in Hitachi Japanese Abstract JO 3245-153A, published Oct. 31, 1991, are toners with hydrotalcite compounds.
Although many charge enhancing additives are known, there continues to be a need for toners with additives, which toners possess many of the advantages illustrated herein. Additionally, there is a need for negative charge enhancing additives which are useful for incorporation into black, and/or colored toner compositions. Moreover, there is a need for colored toner compositions containing certain charge enhancing additives. There is also a need for toner compositions with certain charge enhancing additives, which toners in embodiments thereof may possess acceptable substantially stable triboelectric charging characteristics, and excellent admixing properties. Further, there is a need for toners with certain charge enhancing additives which can be easily and permanently dispersed into toner resin particles. There also is a need for negatively charged black, and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally a need for toner compositions useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Also, there is a need for toner compositions which have the desired triboelectric charge level, for example, from about 10 to about 40 microcoulombs per gram, and preferably from about 10 to about 25 microcoulombs per gram, and admix charging rates of from about 5 to about 60 seconds, and preferably from about 15 to about 30 seconds, as determined by the charge spectrograph, preferably for example at low concentrations, that is for example less than 1 percent, and preferably less than about 0.5 percent of the charge enhancing additive of the present invention. Important advantages associated with the charge additives of the present invention is their white color, thus for example they do not adversely effect the intensity and hue of colored toners with, for example, cyan, magenta, yellow, green, red, blue, brown pigments or mixtures thereof, and that the clay charge additives do not contain toxic heavy metal ions such as chromium.